1. Field of the Invention
The invention relates to an error correction method for the transfer of word-wise arranged data, comprising the following steps:
a. receiving a first number of data words in a first error encoder in order to add thereto a first series of parity words on the basis of a first generator matrix of a first word correction code;
b. delaying said first numbers of data words and first series of parity word by delay times which are all different within each first number and associated first series in order to interleave said words so as to form as many second numbers of words;
c. receiving a second number of words in a second error encoder in order to add thereto a second series of parity words on the basis of a second generator matrix of a second word correction code so as to form a third number of words;
d. word-by-word modulation of said serially linked third numbers of words in order to form channel words which satisfy, by way of added redundancy, predetermined upper limits and lower limits for the admissible intervals between directly successive signal transitions, said channel words being serially concatenated and pair-wise separated by merging bits which also satisfy said upper limits and lower limits in conjunction therewith;
e. demodulation of the channel words and merging bits after the transfer in order to reconstruct said third number of words;
f. reproducing and, if possible and necessary, correcting said second numbers of words on the basis of the second parity check matrix associated with the second generator matrix;
g. de-interleaving said second numbers of words, followed by the reproducing and, if possible and necessary, correcting of said first numbers of data words for a user on the basis of the first parity check matrix associated with the first generator matrix.
2. Description of the Prior Art
Part of the transfer with error correction described above has already been disclosed in Netherlands Patent Application No. 8102441 assigned to the assignee of this application which is based on a Japanese Application No. 567608-80 in the name of Sony Corporation, Shinagawa-ku, Tokyo, Japan. The corresponding U.S. patent applications are Ser. No. 265,465, filed May 20, 1981 and Ser. No. 320,492 filed Nov. 12, 1981, both assigned to Sony, now U.S. Pat. No. 4,413,340. U.S. Pat. No. 4,413,340 is incorporated herein by way of reference. Within a second number of words or a third number of words, a limited number of words can thus be corrected or a further limited number of words can be detected as being incorrect, said limited numbers being given by the minimum Hamming distance of the code taken over the symbols. This will be described in detail hereinafter. If the number of incorrect words within a second or third number of words is larger than the relevant admissible value, the error correction or the detection of incorrect words fails. When the error correction fails, either incorrect words are not corrected or words are incorrectly corrected, or both. If the error detection fails, either correct words are indicated as being incorrect or incorrect words are not indicated as being incorrect, or both. Furthermore the modulation and demodulation has been described in another Netherlands Patent Application No. 8004028, in the name of Applicant. The U.S. Ser. No. is 286,982, filed July 27, 1981, assigned to Sony. This is also incorporated herein by way of reference.